Cylinder 3 misfires and then traction control codes just occured

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by WBLY, Mar 22, 2025.

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  1. WBLY

    WBLY Junior Member

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    I was 100 miles from home on the end of a 9 hour drive in my 2006 Prius when this occurred. The first indicator was the check engine light on. I may have had some engine chugging before that but I would have wrote it off as I was bucking a strong headwind. I immediately pulled into an upcoming gas station. Checked the oil then the code. P0303 - Cylinder 3 misfires. I should have put some fuel injector cleaner in but I didn't. I drove the reset of the way home at a decent speed. After awhile the traction control light would flash when the wind gusted me. It would go away if I let off the gas. Those turned out to be U0123/4/6 and a C0215, codes. I found those this morning.

    So far I have looked at all the spark plugs. They all had large gap between 0.067-0.074". I re-gapped them all at 0.040". Only the cylinder #3 looked a little black. All the other plugs were a nice light brown. There is no coolant missing. The dipstick this morning did not reveal any coolant nor the gas I half expected to see.

    After I re-gapped the plugs, I started up the car with my Autel reader. It showed current Cylinder 1 & 3, misfires as well as the traction code I noted above. The car was idling rough and ran a little better if I gave it some gas. I had a traction control flash this winter that lasted a couple of short drives. I wrote it off as probably ice on the drivers side wheel sensor as It rained then froze the night/day after. I posted about that and one suggestion was to check the 12V standard battery. So I just checked it again with an old fashioned load tester and it showed it was still fine.

    The only thing I was going to try initially was to swap the Cylinder 2 & 3, ignition coils. Now that I also see a cylinder 1 fail code as well as the traction control codes, I'm not so sure where to go next. There must be some electrical relation to the misfires and traction control. Any suggestions on what to pursue next??

    Thanks in Advance!
     

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    #1 WBLY, Mar 22, 2025
  2. WBLY

    WBLY Junior Member

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    I did forget to mention that I was wondering while all the spark plugs gaps were large. I did a piston soak in the first two of the last 3 oil changes. I know I gapped the new plugs for the first piston soak. Why would the gap widen in say 15,000 miles?
     
    #2 WBLY, Mar 22, 2025
  3. Tombukt2

    Tombukt2 Senior Member

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    Generally with these modern iridium plugs and all that . Maybe get a new set of SK16s or 20s pick your poison you 11 for the gap code and put those in and see what happens and the rest of the business is communication codes that's generally 12 volt related or a disconnect related loose wire etc
     
    #3 Tombukt2, Mar 22, 2025
  4. dolj

    dolj Senior Member

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    You installed cheap eBay or Amazon plugs that claim to be iridium but really are just reboxed copper cores?
     
    #4 dolj, Mar 22, 2025
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    My first thought is that you received a set of counterfeit spark plugs. Where did you buy them?

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Mar 22, 2025
  6. WBLY

    WBLY Junior Member

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    Mine were eBay. Why are these: "Maybe get a new set of SK16s or 20s pick your poison you 11 for the gap code " better? What's the best source,; NAPA?
     
    #6 WBLY, Mar 23, 2025
  7. WBLY

    WBLY Junior Member

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    Yeah, they were eBay. Were the best place to get good ones?
     
    #7 WBLY, Mar 23, 2025
  8. dolj

    dolj Senior Member

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    Any trusted brick-and-mortar store or a genuine online Toyota dealer.
     
    #8 dolj, Mar 23, 2025
  9. AzWxGuy

    AzWxGuy Weather Guy

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    One other item that bears repeating is the relative maintenance-free nature of iridium sparkplugs. Iridium metal is hard and brittle with a very high melting point. The plugs are gapped once at the factory and should never need adjustment in their 120,000 mile life. All those days of scraping, brushing, and gapping sparkplugs are behind us.
     
    #9 AzWxGuy, Mar 23, 2025
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  10. Tombukt2

    Tombukt2 Senior Member

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    There are ways you can look at the silver and markings on the plug and determine fakes from originals The models I listed above are the two factory plugs listed for the car I do believe in the owner's manual that u11 of a denso plug I believe means 044 gap You can look it up on the denso site what all of the SK16 u11 means in US text It's very simple to understand The brand is not a make or break thing it's the heat range the projection of the tip and the gap and that they're well made there's no big argument among NGK and denso plugs. I put some cheapo plugs that came with a set of coils for a V6 Mercedes The markings on the plugs look just like NGK not NGK fakes or trying to be so. But I will say they were iridium they weren't the extended long life they didn't have the landing pad for the spark on the part that you bend I can't remember the name of that that has the u in it in denso. Those cheap things ran 90K. And looked good doing it and on removal no brown streaks no blow by nothing not suggesting this but there were no problems and I do believe another set was put back in and then the car was run into and totaled.
     
    #10 Tombukt2, Mar 23, 2025
  11. ChapmanF

    ChapmanF Senior Member

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    One of the best ways around for someone to embark on a wild goose chase is by assuming that any two warnings arising around the same time must be related. Sometimes there does turn out to be a connection and a lot of times they're just two things that went wrong with the car around the same time. Just following the troubleshooting instructions for the warnings you've got is usually the right approach. If there is, in fact, some connection between the underlying causes, you'll find that out when you find them.
     
    #11 ChapmanF, Mar 23, 2025
  12. WBLY

    WBLY Junior Member

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    It took me a bit to get the same NGK 4996/IFR5T11 plugs that had previously lasted 210+K miles. They looked way worse than these knockoff Genuine Toyota Denso plugs did after 18K miles but didn't cause misfires. Now the engine runs fine. I haven't put any significant miles on it yet but there are no check engine or traction control, lights or codes so far.
     
    #12 WBLY, Mar 24, 2025
  13. Brian1954

    Brian1954 Senior Member

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    Where did you buy the new NGK spark plugs from?
     
    #13 Brian1954, Mar 24, 2025
  14. WBLY

    WBLY Junior Member

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    O'Reilly auto stores. There the closest chain store to me. $13.49 per plug.
     
    #14 WBLY, Mar 24, 2025
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